The invention relates to a method of manufacturing electroluminescent semiconductor devices, particularly but not exclusively a method of manufacturing semiconductor laser devices, and further relates to electroluminescent semiconductor devices manufactured by such a method.
From IEEE Journal of Quantum Electronics, vol. QE 13, No. 8, August 1977, pp. 628-631, a method is known in which epitaxial layers of n-type gallium aluminum arsenide, p-type gallium arsenide (the active layer), p-type gallium aluminum arsenide and p-type gallium arsenide are formed successively on a substrate of n-type gallium arsenide.
The width of the active regions is then established by etching and the regions are insulated from each other by the selective deposition of polycrystalline gallium arsenide phosphide having a high resistivity. The length of the active regions is then fixed by an etching treatment and the mirror surfaces are formed.
As used herein, the terms "active layer" and "active region" are to be understood to mean a layer and a region respectively in which radiation can be generated.
A disadvantage of the formation of mirror surface by etching is that the said layers often have different etching rates and, in particular, accelerated etching may occur near the interfaces between the layers. Also, the etched surface may show irregularities so that the operation of the device may be adversely influenced.
In practice, therefore, the mirror surfaces are often obtained not by etching but by cleaving the crystal formed by the layers. However, a disadvantage of cleaving is that integration of the active regions with other active or passive components in one crystal is substantially impossible and coupling of the light between discrete active or passive components is a very exacting task. Furthermore, covering the mirrors with a protective layer can be carried out only after cleaving and hence is very time-consuming.